In this reporting period, papers dealing with the following projects appeared in print: (1) Theory of single molecule fluorescence spectroscopy of two state systems, (2) first passage time in phase space for the strong collision model, (3) Kramers like turnover of the rates of activation less processes. Only the first project will be briefly described here. Recent technological advances have made it possible to study the behavior of single molecules in solution using a variety of techniques including single molecule spectroscopy. Since such experiments, unlike those performed on bulk systems, lead to results that fluctuate, they require novel kinds of theories for their interpretation. In our first piece of work in this new area, we derived an analytic expression for the probability distribution of the amplitudes of the exponentials in the fluorescence decay observed in experiments of finite duration involving single DNA and RNA molecules. This result allows one to extract the rates of conformational changes from such experiments. Since bulk experiments are determined only by the equilibrium populations of the different conformers, single molecule experiments, when properly analyzed, lead to new kinds of information( e.g. the rates of conformational changes). - single molecule spectroscopy, fluorescence, rate processes